It can hardly have escaped anyone's attention over the first week at Wimbledon that there have been an awful lot of late nights. Andy Murray's 11.02pm finish against Marcos Baghdatis on Saturday night was the latest in the Championships' history; Rafael Nadal's defeat to Lukas Rosol came past 10pm and even Roger Federer's comeback victory over Julien Benneteau was at 9.20pm.

The main reason for these late night finishes, of course, is the retractable roof, which was installed at an estimated cost of £80m and which opened in 2009. In the first two years, good weather meant it was barely required but in the past seven days it has been called into action on a regular basis. Television companies love it because they can plan their schedules with absolute certainty and fans splashing out good money on tickets also know that they will not be rained out.

Murray's match with Baghdatis was watched by more than 8 million people on BBC on Saturday night, highlighting the popularity of the sport. ITV was ecstatic with the figures for its first year of French Open coverage and the evening matches at Wimbledon have all attracted an impressive share of the viewing figures.

The roof has not been to everyone's liking. Rafael Nadal was surprised at how long it took to close it and begin playing again — it was 43 minutes that night but the average is around 30 minutes — while conditions under the roof become heavier and slower, even if the absence of any wind makes life easier.

The All England Club was criticised for closing the roof for a couple of matches even when it was sunny outside — a decision it took, it said, because of a dodgy weather forecast — and it insists it remains an outdoor event. But much of the talk behind the scenes has been about whether the increasing use of the roof means we are creeping towards night tennis.

The US Open and Australian Open have had scheduled night tennis for many years and the French Open is set to follow suit once it has installed a roof over an expanded main court, in 2017, leaving Wimbledon as the only grand slam event not to be officially playing at night.

Part of the reason is that the local council of Merton insists on play finishing at 11pm. Public transport does not run much past midnight from the nearby stations and the idea of 15,000 fans milling into Wimbledon Village around midnight has met with understandable local opposition. But shortly after Murray's match had finished, Merton Council Tweeted: "Great win for Murray. We will always be flexible and take (a) common-sense approach. We had pre-arranged with AELTC they would use their discretion."

The roof is one of many changes the game has seen. Players are fitter than ever and as any regular fan will appreciate, the courts at Wimbledon are slower. The days of John McEnroe, Boris Becker and Pete Sampras serving and volleying and rushing the net are long gone. "Serve and volley? What's that?" McEnroe said on Saturday. And as Maria Sharapova said last week: "When I look back to when I won here in 2004, it was much faster than it is now. Look back five years before that and it was another story."

Eddie Seaward, the long-serving head groundsman, said recently that the courts have not been slowed but that the bounce is higher, because the ground is harder. "It gives each player around a tenth of a second extra to react," he said. But Roger Federer said: "obviously they're not the fastest courts anymore".

Advancements in racket technology and in particular to the strings mean that it is easier for players to hit hard from the baseline, with more spin. Combined with their improved athleticism, they can do it for longer.

Longer rallies mean players are taking more time to recover for the next point, making longer matches. Gilbert Ysern, the French Open tournament director, calculated this year that matches lasted, on average, around 30 minutes longer than in 2011 and the trend appears to be similar at Wimbledon. Over the first three rounds this year, there have been 26 five-set matches. Over the past 10 years, the average for the entire tournament is 23.5 but in two of the past three years, there were 28 and 30.

The nine-times singles champion Martina Navratilova has called for a tie-break in the final set at Wimbledon, as happens at the US Open. "No tie-breaks was the tradition [but] that doesn't make it right," she said on Twitter. In 2001, Centre Court moved its start times back from 2pm to 1pm and many feel it now needs to go to 12pm. But there is a fear that if the grass is used too much, especially under the roof, its quality will be affected.

It is a difficult balance for Wimbledon, a tournament that has always prided itself on staying ahead of the game while it maintains its traditions. Tennis is changing; perhaps Wimbledon needs to follow suit.